Abstract

We report on the dependence of the lattice parameter on thickness and grain size in nanogranular Nbthin filmsdeposited on Si (100) substrates by using dc magnetron sputtering. The lattice parameter is found to exponentially increase with decreasing thickness as well as grain size. We analyze the lattice expansion in terms of the excess free volume in the grain boundaries, which is found to decrease with the grain size in large thickness limit. The thickness dependence of the lattice expansion and the grain size dependence of the excess free volume are discussed in terms of the oxygen content in the grain boundaries.

Received 21 December 2007Accepted 17 March 2008Published online 28 May 2008

Acknowledgments:

We acknowledge Uma Shanker for his help in the x-ray diffraction measurements at the Advanced Center for Material Science (ACMS) in IITK. A.K.G. acknowledges partial funding from the DST of the Government of India. D.H. acknowledges the financial support from the CSIR.